Even tungsten etch for high aspect ratio trenches

ABSTRACT

Methods of evenly etching tungsten liners from high aspect ratio trenches are described. The methods include ion bombardment of a patterned substrate having high aspect ratio trenches. The ion bombardment includes fluorine-containing ions and the ion bombardment may be stopped before breaking through the horizontal liner portion outside the trenches but near the opening of the trenches. The methods then include a remote plasma etch using plasma effluents formed from a fluorine-containing precursor. Plasma effluents from the remote plasma are flowed into a substrate processing region where the plasma effluents react with the tungsten. The plasmas effluents react with exposed surfaces and remove tungsten from outside the trenches and on the sidewalls of the trenches. The plasma effluents pass through an ion suppression element positioned between the remote plasma and the substrate processing region.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Prov. Pat. App. No.61/917,433 filed Dec. 18, 2013, and titled “EVEN TUNGSTEN ETCH FOR HIGHASPECT RATIO TRENCHES” by Wang et al., which is hereby incorporatedherein in its entirety by reference for all purposes.

FIELD

Embodiments of the invention relate to evenly etching tungsten fromtrench sidewalls.

BACKGROUND

Integrated circuits are made possible by processes which produceintricately patterned material layers on substrate surfaces. Producingpatterned material on a substrate requires controlled methods forremoval of exposed material. Chemical etching is used for a variety ofpurposes including transferring a pattern in photoresist into underlyinglayers, thinning layers or thinning lateral dimensions of featuresalready present on the surface. Often it is desirable to have an etchprocess which etches one material faster than another helping e.g. apattern transfer process proceed. Such an etch process is said to beselective of the first material. As a result of the diversity ofmaterials, circuits and processes, etch processes have been developedthat selectively remove one or more of a broad range of materials.

Dry etch processes are often desirable for selectively removing materialfrom semiconductor substrates. The desirability stems from the abilityto gently remove material from miniature structures with minimalphysical disturbance. Dry etch processes also allow the etch rate to beabruptly stopped by removing the gas phase reagents. Some dry-etchprocesses involve the exposure of a substrate to remote plasmaby-products formed from one or more precursors. For example, remoteplasma excitation of ammonia and nitrogen trifluoride enables siliconoxide to be selectively removed from a patterned substrate when theplasma effluents are flowed into the substrate processing region. Remoteplasma etch processes have recently been developed to selectively removea variety of dielectrics relative to one another. However, fewerdry-etch processes have been developed to remove refractory metals liketungsten.

Methods are needed to etch tungsten selectively and evenly frompatterned substrates using dry etch processes.

SUMMARY

Methods of evenly etching tungsten liners from high aspect ratiotrenches are described. The methods include ion bombardment of apatterned substrate having high aspect ratio trenches. The ionbombardment includes fluorine-containing ions and the ion bombardmentmay be stopped before breaking through the horizontal liner portionoutside the trenches but near the opening of the trenches. The methodsthen include a remote plasma etch using plasma effluents formed from afluorine-containing precursor. Plasma effluents from the remote plasmaare flowed into a substrate processing region where the plasma effluentsreact with the tungsten. The plasmas effluents react with exposedsurfaces and remove tungsten from outside the trenches and on thesidewalls of the trenches. The plasma effluents pass through an ionsuppression element positioned between the remote plasma and thesubstrate processing region.

Embodiments include methods of etching tungsten. The methods includetransferring a patterned substrate into a substrate processing region.The patterned substrate has a tungsten lining layer coating a highaspect ratio trench having a depth more than five times a width of thehigh aspect ratio trench. The methods further include flowing a firstfluorine-containing precursor into the substrate processing region whileapplying a bias plasma power to bombard the patterned substrate withfluorine-containing ions. The methods further include flowing a secondfluorine-containing precursor into a remote plasma region fluidlycoupled to a substrate processing region via perforations in theperforated plate. The methods further include forming a remote plasma inthe remote plasma region to produce plasma effluents from the secondfluorine-containing precursor and flowing the plasma effluents into thesubstrate processing region through the perforations. The methodsfurther include etching the tungsten lining layer. After etching thetungsten lining layer, a top thickness of the tungsten lining layermeasured on a sidewall of the high aspect ratio trench near the openingof the trench is within 20% of a bottom thickness of the tungsten lininglayer measured on the sidewall of the high aspect ratio trench near thebottom of the trench.

Embodiments include methods of etching tungsten. The methods includetransferring a patterned substrate into a substrate processing region.The patterned substrate has a tungsten lining layer coating two adjacentstacks and a high aspect ratio trench between the two adjacent stacks.The methods further include flowing a first fluorine-containingprecursor into the substrate processing region while applying localplasma power which accelerates fluorine-containing ions toward thesubstrate. The methods further include flowing a secondfluorine-containing precursor into a remote plasma region fluidlycoupled to a substrate processing region via perforations in theperforated plate. The methods further include forming a remote plasma inthe remote plasma region to produce plasma effluents from the secondfluorine-containing precursor and flowing the plasma effluents into thesubstrate processing region through the perforations. The methodsfurther include etching the tungsten lining layer. Etching the tungstenlining layer reduces a thickness of the tungsten lining layer on asidewall of the high aspect ratio trench.

Embodiments include methods of etching tungsten. The methods includetransferring a patterned substrate into a substrate processing region.The patterned substrate has a tungsten lining layer coating a highaspect ratio trench having a depth more than five times a width of thehigh aspect ratio trench. The methods further include flowing afluorine-containing precursor into the substrate processing region whileapplying local plasma power capacitively between a perforated plate anda substrate susceptor supporting the patterned substrate to create andaccelerate fluorine-containing ions toward the patterned substrate. Themethods further include flowing nitrogen trifluoride into a remoteplasma region fluidly coupled to a substrate processing region viaperforations in the perforated plate. The methods further includeforming a remote plasma in the remote plasma region to produce plasmaeffluents from the nitrogen trifluoride and flowing the plasma effluentsinto the substrate processing region through the perforations. Themethods further include etching the tungsten lining layer. Etching thetungsten lining layer reduces a thickness of the tungsten lining layeron a sidewall of the high aspect ratio trench at a top rate near theoutermost portion of the sidewall of the high aspect ratio trench whichis within 20% of a bottom rate near the innermost portion the sidewallof the high aspect ratio trench.

Additional embodiments and features are set forth in part in thedescription that follows, and in part will become apparent to thoseskilled in the art upon examination of the specification or may belearned by the practice of the disclosed embodiments. The features andadvantages of the disclosed embodiments may be realized and attained bymeans of the instrumentalities, combinations, and methods described inthe specification.

DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the disclosedembodiments may be realized by reference to the remaining portions ofthe specification and the drawings.

FIG. 1 is a flow chart of a tungsten liner etch process according toembodiments.

FIGS. 2A-2D are cross-sectional schematics of tungsten on high aspectratio trenches before and after tungsten etch processes according toembodiments.

FIG. 3A shows a substrate processing chamber according to embodiments.

FIG. 3B shows a showerhead of a substrate processing chamber accordingto embodiments.

FIG. 4 shows a substrate processing system according to embodiments.

In the appended figures, similar components and/or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

DETAILED DESCRIPTION

Methods of evenly etching tungsten liners from high aspect ratiotrenches are described. The methods include ion bombardment of apatterned substrate having high aspect ratio trenches. The ionbombardment includes fluorine-containing ions and the ion bombardmentmay be stopped before breaking through the horizontal liner portionoutside the trenches but near the opening of the trenches. The methodsthen include a remote plasma etch using plasma effluents formed from afluorine-containing precursor. Plasma effluents from the remote plasmaare flowed into a substrate processing region where the plasma effluentsreact with the tungsten. The plasmas effluents react with exposedsurfaces and remove tungsten from outside the trenches and on thesidewalls of the trenches. The plasma effluents pass through an ionsuppression element positioned between the remote plasma and thesubstrate processing region.

In order to better understand and appreciate the invention, reference isnow made to FIG. 1 which is a flow chart of a tungsten liner (a.k.a.tungsten lining layer) etch process 100 according to embodiments. Priorto the first operation, the tungsten liner is formed on a substrate. Thetungsten liner may be conformal over features present on a patternedsubstrate surface. The features include a high aspect ratio trench whosedepth exceeds its width by a multiplicative factor of five, ten orfifteen according to embodiments. The patterned substrate is thendelivered into a substrate processing region (operation 110). In anotherembodiment, the tungsten liner may be formed after delivering thesubstrate to the substrate processing region.

A flow of nitrogen trifluoride is introduced into the substrateprocessing region (operation 120). Plasma power is supplied to thesubstrate processing region to form a local plasma. The local plasma maybe an inductively coupled plasma or a capacitively coupled plasma. Ineither case, a bias power is applied to accelerate fluorine-containingions formed from the nitrogen trifluoride towards the patternedsubstrate. A separate power source may be used to bias the inductivelycoupled plasma relative to the patterned substrate. In the case of acapacitively coupled plasma, the preferred embodiment, the capacitiveplasma power already biases the fluorine-containing ions relative to thesubstrate. Other sources of fluorine may be used to augment or replacethe nitrogen trifluoride. In general, a fluorine-containing precursormay be flowed into the plasma region and the fluorine-containingprecursor comprises at least one precursor selected from the groupconsisting of atomic fluorine, diatomic fluorine, bromine trifluoride,chlorine trifluoride, nitrogen trifluoride, hydrogen fluoride, sulfurhexafluoride and xenon difluoride. The patterned substrate is bombarded(a.k.a. sputtered) with the fluorine-containing ions in operation 125.

A flow of nitrogen trifluoride is then introduced into a plasma regionseparate from the processing region (operation 130) in a preferredembodiment. Other sources of fluorine may be used to augment or replacethe nitrogen trifluoride. In general, a fluorine-containing precursormay be flowed into the plasma region and the fluorine-containingprecursor comprises at least one precursor selected from the groupconsisting of atomic fluorine, diatomic fluorine, bromine trifluoride,chlorine trifluoride, nitrogen trifluoride, hydrogen fluoride, sulfurhexafluoride and xenon difluoride. Remote plasma power is applied to theremote plasma region to excite the fluorine-containing precursor (e.g.the nitrogen trifluoride) and form plasma effluents in operation 130 aswell.

The separate plasma region may be referred to as a remote plasma regionfor all etch processes described herein and may be within a distinctmodule from the processing chamber or a compartment within theprocessing chamber. The separate plasma region may is fluidly coupled tothe substrate processing region by through-holes in a showerheaddisposed between the two regions. The hardware just described may alsobe used in all processes discussed herein. The remote plasma region maybe a capacitively-coupled plasma region, in embodiments, and may bedisposed remote from the substrate processing region of the processingchamber. For example, the capacitively-coupled plasma region (and theremote plasma region in general) may be separated from the substrateprocessing region by the showerhead.

The plasma effluents formed in the remote plasma region are then flowedinto the substrate processing region (operation 135). The tungsten lineron the substrate is evenly etched (also in operation 135) such thattungsten liner on the sidewalls of the high aspect ratio trench issubstantially evenly removed. The reactive chemical species and anyprocess effluents are removed from the substrate processing region andthen the substrate is removed from the substrate processing region(operation 145).

In each local plasma and/or remote plasma described herein, the flows ofthe precursors into the remote plasma region may further include one ormore relatively inert gases such as He, N₂, Ar. The inert gas can beused to improve plasma stability, ease plasma initiation, and improveprocess uniformity. Argon is helpful, as an additive, to promote theformation of a stable plasma. Process uniformity is generally increasedwhen helium is included. These additives are present in embodimentsthroughout this specification. Flow rates and ratios of the differentgases may be used to control etch rates and etch selectivity.

The following flow rates apply to either the local plasma portion oftungsten liner etch process 100 (i.e. operations 120-125) or the remoteplasma portion of tungsten liner etch process 100 (i.e. operations130-135). The precursor used during the local plasma portion may bereferred to as the first fluorine-containing precursor and the precursorused during the remote plasma portion may be referred to as the secondfluorine-containing precursor. The first fluorine-containing precursormay be the same as the second fluorine-containing precursor according toembodiments. In embodiments, the fluorine-containing gas (e.g. NF₃) issupplied at a flow rate of between about 25 sccm (standard cubiccentimeters per minute) and 400 sccm, He at a flow rate of between about0 slm (standard liters per minute) and 3 slm, and Ar at a flow rate ofbetween about 0 slm and 3 slm. The fluorine-containing precursor may besupplied at a flow rate between about 25 sccm and about 400 sccm,between about 50 sccm and about 300 sccm, between about 75 sccm andabout 200 sccm or preferably between about 125 sccm and about 175 sccmaccording to embodiments.

The local plasma power (or the bias plasma power) may be appliedcapacitively and may be between about 10 watts and about 2000 watts,between about 30 watts and about 1500 watts, between about 100 watts andabout 1000 watts, between about 150 watts and about 700 watts orpreferably between about 200 watts and 500 watts according toembodiments. The local plasma power may be between about 20 watts andabout 500 watts in embodiments. The local plasma power may be appliedusing radio frequencies (e.g. 13.56 MHz). The pressure in the substrateprocessing region during application of the local plasma power or thebias plasma power may be between about 0.01 Torr and about 5 Torr,between about 0.05 Torr and about 2 Torr or preferably between about 0.1Torr and about 1 Torr in embodiments. The temperature of the substratemay be between about 30° C. and about 400° C., between about 40° C. andabout 350° C., between about 60° C. and about 280° C., between about 80°C. and about 250° C. or preferably between about 100° C. and about 160°C. in embodiments, during application of local or bias plasma power.

The operation of forming the remote plasma occurs after the operation ofapplying the bias plasma power or local plasma power in embodiments. Theremote plasma power may be applied capacitively and may be between about10 watts and about 2500 watts, between about 30 watts and about 2000watts, between about 100 watts and about 1500 watts, between about 300watts and about 1000 watts or between about 400 watts and 800 wattsaccording to embodiments. The remote plasma power may be greater than 50watts in embodiments. The remote plasma power may be applied using radiofrequencies (e.g. 13.56 MHz). During this portion of the process, thepressure in the substrate processing region is about the same as thepressure in the substrate processing region, according to embodiments,in all tungsten liner etch processes described herein. The pressure inthe substrate processing region and/or the remote plasma region duringapplication of the remote plasma power may be between about 0.1 Torr andabout 50 Torr, between about 0.5 Torr and about 20 Torr or preferablybetween about 1 Torr and about 10 Torr in embodiments. The temperatureof the substrate may be between about 30° C. and about 400° C., betweenabout 40° C. and about 350° C., between about 60° C. and about 280° C.,between about 80° C. and about 250° C. or preferably between about 100°C. and about 160° C. in embodiments, during application of remote plasmapower. No local plasma power (or no bias plasma power) is applied duringthe operation of forming the remote plasma according to embodiments.

In embodiments and operations employing a remote plasma, an ionsuppressor as described in the exemplary equipment section may be usedto provide radical and/or neutral species for selectively etchingsubstrates. The ion suppressor may also be referred to as an ionsuppression element. In embodiments, for example, the ion suppressor isused to filter fluorine-containing plasma effluents to selectively etchtungsten. The ion suppressor may be included in each exemplary processdescribed herein. Using the plasma effluents, an etch rate selectivityof tungsten to a wide variety of materials may be achieved.

The ion suppressor may be used to provide a reactive gas having a higherconcentration of radicals than ions. The ion suppressor functions todramatically reduce or substantially eliminate ionically charged speciestraveling from the plasma generation region to the substrate. Theelectron temperature may be measured using a Langmuir probe in thesubstrate processing region during excitation of a plasma in the remoteplasma region on the other side of the ion suppressor. In embodiments,the electron temperature may be less than 0.5 eV, less than 0.45 eV,less than 0.4 eV, or preferably less than 0.35 eV. These extremely lowvalues for the electron temperature are enabled by the presence of theshowerhead and/or the ion suppressor positioned between the substrateprocessing region and the remote plasma region. Uncharged neutral andradical species may pass through the openings in the ion suppressor toreact at the substrate. Because most of the charged particles of aplasma are filtered or removed by the ion suppressor, the substrate isnot necessarily biased during the etch process. Such a process usingradicals and other neutral species can reduce plasma damage compared toconventional plasma etch processes that include sputtering andbombardment. The ion suppressor helps control the concentration of ionicspecies in the reaction region at a level that assists the process.Embodiments of the present invention are also advantageous overconventional wet etch processes where surface tension of liquids cancause bending and peeling of small features.

In order to further appreciate the invention, reference is now made toFIGS. 2A-2D, which are cross-sectional schematics of tungsten on highaspect ratio trenches before and after tungsten etch processes accordingto embodiments. A patterned substrate 200-1 begins with high aspectratio structures as shown in FIG. 2A. A conformal tungsten liner 210-1is present on the high aspect ratio structures prior to the etchprocesses described herein. FIGS. 2B-2C show the profile of residualtungsten if only portions of tungsten liner etch process 100 are carriedout. FIG. 2B shows the tungsten liner 210-2 profile after an etchprocess using only operations 130-135 are performed on patternedsubstrate 200-1. Operations 130-135 depend on the chemical reactions ofneutral fluorine radicals with tungsten liner 210-1 to form tungstenliner 210-2. Tungsten liner 210-2 is undesirably removed at a greaterrate near the opening of the high aspect ratio trench compared to theremoval rate deep within the trench. This observation is likelyattributed to the reaction kinetics of the chemical reaction takingplace to remove the tungsten. FIG. 2C shows the tungsten liner 210-3profile after an etch process using only operations 120-125. Operations120-125 provide ions and physical bombardment of patterned substrate200-1 which has been found to also result in an undesirable preferentialremoval of tungsten from near the opening of the trench. Patternedsubstrate 200-1 may even lose some material underneath tungsten liner210-1, due to the ballistic nature of the process, to form patternedsubstrate 200-2.

FIG. 2D shows the tungsten liner 210-4 profile after the completetungsten liner etch process 100. Obviously, the duration of the localplasma portion of tungsten liner etch process 100 is shorter in thecomplete tungsten liner etch 100 compared to the local plasma processwhich resulted in the profile depicted in FIG. 2B. However, the effectof the bombardment is to increase the removal rate of the remote plasmaportion of tungsten liner etch process 100 and to make the processproceed more evenly. The removal rate near the top (i.e. near theopening of the trench) nearly matches the removal rate near the bottom(i.e. deep within the trench). The process may leave some tungsten onthe top of the pylons on either side of the trench or the tungsten ontop of the pylons may be removed (not shown) according to embodiments.Either portion of tungsten liner etch process, carried out alone,results in a higher removal rate near the opening of the trench,however, combining both processes in the proper order results in adesirable even sidewall removal rate up and down the trench sidewall.

FIGS. 2A-2D show patterned substrate 200 as one homogeneous material.Generally speaking, the high aspect ratio trench may be formed betweenpylons of a material which differs from the rest of the substrate. Thepylons themselves may actually be stacks of multiple materials arrangedin layers according to embodiments. Even more generally, the high aspectratio trench may be formed into a substrate so the sidewalls are notformed on pylons at all, but on walls of a trench burrowed into the bulksubstrate itself. “Substrate” will be used to refer to anything belowthe tungsten liner and so will include deposited and patterned layers,when present, on the surface of the bulk substrate (e.g. a siliconwafer). The high aspect ratio trench is formed between two pylonsaccording to embodiments. One or both of the two adjacent stacks mayinclude at least ten alternating layers of dielectric (e.g. siliconoxide) and tungsten in embodiments.

The high aspect ratio trench may have a variety of dimensions. The highaspect ratio trench may have a depth which exceeds its width by amultiplicative factor of five, eight, ten or fifteen according toembodiments. The depth of the high aspect ratio trench may be greaterthan one micron, greater than 1.5 μm or greater than 2 μm according toembodiments. The width of the high aspect ratio trench may be less thanone hundred nanometers, less than 75 nm, less than 50 nm or less than 30nm in embodiments.

The effect of etch during or after tungsten liner etch process 100 willnow be described. Following the etch, a top sidewall thickness of thetungsten lining layer measured on a sidewall of the high aspect ratiotrench near the opening of the trench may be within 20% of a bottomsidewall thickness of the tungsten lining layer measured on the sidewallof the high aspect ratio trench near the bottom of the trench. Onceagain, bottom and top are defined as deeper within the trench and closerto the opening of the trench respectively. The bottom sidewall thicknessmay be measured within the bottom 10% of the depth of the trenchmeasured linearly and not by volume. Similarly, the top sidewallthickness may be measured within the top 10% of the depth of the trench.Etching the tungsten lining layer may reduce a thickness of the tungstenlining layer at a top rate near the outermost portion of the sidewall ofthe high aspect ratio trench which is within 20% of a bottom rate nearthe innermost portion of the sidewall of the high aspect ratio trench.Outermost portion and innermost portion are again defined as the top 10%and bottom 10% of the depth of the trench, respectively.

Additional process parameters are disclosed in the course of describingan exemplary processing chamber and system.

Exemplary Processing System

Processing chambers that may implement embodiments of the presentinvention may be included within processing platforms such as theCENTURA® and PRODUCER® systems, available from Applied Materials, Inc.of Santa Clara, Calif.

FIG. 3A is a substrate processing chamber 1001 according to embodiments.A remote plasma system 1010 may process a fluorine-containing precursorwhich then travels through a gas inlet assembly 1011. Two distinct gassupply channels are visible within the gas inlet assembly 1011. A firstchannel 1012 carries a gas that passes through the remote plasma system1010 (RPS), while a second channel 1013 bypasses the remote plasmasystem 1010. Either channel may be used for the fluorine-containingprecursor, in embodiments. On the other hand, the first channel 1012 maybe used for the process gas and the second channel 1013 may be used fora treatment gas. The lid (or conductive top portion) 1021 and aperforated partition 1053 are shown with an insulating ring 1024 inbetween, which allows an AC potential to be applied to the lid 1021relative to perforated partition 1053. The AC potential strikes a plasmain chamber plasma region 1020. The process gas may travel through firstchannel 1012 into chamber plasma region 1020 and may be excited by aplasma in chamber plasma region 1020 alone or in combination with remoteplasma system 1010. If the process gas (the fluorine-containingprecursor) flows through second channel 1013, then only the chamberplasma region 1020 is used for excitation. The combination of chamberplasma region 1020 and/or remote plasma system 1010 may be referred toas a remote plasma system herein. The perforated partition (alsoreferred to as a showerhead) 1053 separates chamber plasma region 1020from a substrate processing region 1070 beneath showerhead 1053.Showerhead 1053 allows a plasma present in chamber plasma region 1020 toavoid directly exciting gases in substrate processing region 1070, whilestill allowing excited species to travel from chamber plasma region 1020into substrate processing region 1070.

Showerhead 1053 is positioned between chamber plasma region 1020 andsubstrate processing region 1070 and allows plasma effluents (excitedderivatives of precursors or other gases) created within remote plasmasystem 1010 and/or chamber plasma region 1020 to pass through aplurality of through-holes 1056 that traverse the thickness of theplate. The showerhead 1053 also has one or more hollow volumes 1051which can be filled with a precursor in the form of a vapor or gas (suchas a fluorine-containing precursor) and pass through small holes 1055into substrate processing region 1070 but not directly into chamberplasma region 1020. Showerhead 1053 is thicker than the length of thesmallest diameter 1050 of the through-holes 1056 in this embodiment. Thelength 1026 of the smallest diameter 1050 of the through-holes may berestricted by forming larger diameter portions of through-holes 1056part way through the showerhead 1053 to maintain a significantconcentration of excited species penetrating from chamber plasma region1020 to substrate processing region 1070. The length of the smallestdiameter 1050 of the through-holes 1056 may be the same order ofmagnitude as the smallest diameter of the through-holes 1056 or less inembodiments.

Showerhead 1053 may be configured to serve the purpose of an ionsuppressor as shown in FIG. 3A. Alternatively, a separate processingchamber element may be included (not shown) which suppresses the ionconcentration traveling into substrate processing region 1070. Whether ashowerhead or an ion suppressor is being described, the item may bereferred to as a perforated plate having perforations which pass andneutralize some or substantially all of the plasma effluents. Lid 1021and showerhead 1053 may function as a first electrode and secondelectrode, respectively, so that lid 1021 and showerhead 1053 mayreceive different electric voltages. In these configurations, electricalpower (e.g., RF power) may be applied to lid 1021, showerhead 1053, orboth. For example, electrical power may be applied to lid 1021 whileshowerhead 1053 (serving as ion suppressor) is grounded. The substrateprocessing system may include a RF generator that provides electricalpower to the lid and/or showerhead 1053. The voltage applied to lid 1021may facilitate a uniform distribution of plasma (i.e., reduce localizedplasma) within chamber plasma region 1020. To enable the formation of aplasma in chamber plasma region 1020, insulating ring 1024 mayelectrically insulate lid 1021 from showerhead 1053. Insulating ring1024 may be made from a ceramic and may have a high breakdown voltage toavoid sparking. Portions of substrate processing chamber 1001 near thecapacitively-coupled plasma components just described may furtherinclude a cooling unit (not shown) that includes one or more coolingfluid channels to cool surfaces exposed to the plasma with a circulatingcoolant (e.g., water).

In the embodiment shown, showerhead 1053 may distribute (viathrough-holes 1056) process gases which contain fluorine or plasmaeffluents of such process gases upon excitation by a plasma in chamberplasma region 1020. In embodiments, the process gas introduced into theremote plasma system 1010 and/or chamber plasma region 1020 may containfluorine (e.g. F₂, NF₃ or XeF₂). The process gas may also include acarrier gas such as helium, argon, nitrogen (N₂), etc. Plasma effluentsmay include ionized or neutral derivatives of the process gas and mayalso be referred to herein as radical-fluorine referring to the atomicconstituent of the process gas introduced.

Through-holes 1056 are configured to suppress the migration ofionically-charged species out of the chamber plasma region 1020 whileallowing uncharged neutral or radical species to pass through showerhead1053 into substrate processing region 1070. These uncharged species mayinclude highly reactive species that are transported with less-reactivecarrier gas by through-holes 1056. As noted above, the migration ofionic species by through-holes 1056 may be reduced, and in someinstances completely suppressed. Controlling the amount of ionic speciespassing through showerhead 1053 provides increased control over the gasmixture brought into contact with the underlying wafer substrate, whichin turn increases control of the deposition and/or etch characteristicsof the gas mixture. For example, adjustments in the ion concentration ofthe gas mixture can alter the etch selectivity.

In embodiments, the number of through-holes 1056 may be between about 60and about 2000. Through-holes 1056 may have a variety of shapes but aremost easily made round. The smallest diameter 1050 of through-holes 1056may be between about 0.5 mm and about 20 mm or between about 1 mm andabout 6 mm in embodiments. There is also latitude in choosing thecross-sectional shape of through-holes, which may be made conical,cylindrical or combinations of the two shapes. The number of small holes1055 used to introduce unexcited precursors into substrate processingregion 1070 may be between about 100 and about 5000 or between about 500and about 2000 in different embodiments. The diameter of the small holes1055 may be between about 0.1 mm and about 2 mm.

Through-holes 1056 may be configured to control the passage of theplasma-activated gas (i.e., the ionic, radical, and/or neutral species)through showerhead 1053. For example, the aspect ratio of the holes(i.e., the hole diameter to length) and/or the geometry of the holes maybe controlled so that the flow of ionically-charged species in theactivated gas passing through showerhead 1053 is reduced. Through-holes1056 in showerhead 1053 may include a tapered portion that faces chamberplasma region 1020, and a cylindrical portion that faces substrateprocessing region 1070. The cylindrical portion may be proportioned anddimensioned to control the flow of ionic species passing into substrateprocessing region 1070. An adjustable electrical bias may also beapplied to showerhead 1053 as an additional means to control the flow ofionic species through showerhead 1053.

Alternatively, through-holes 1056 may have a smaller inner diameter (ID)toward the top surface of showerhead 1053 and a larger ID toward thebottom surface. In addition, the bottom edge of through-holes 1056 maybe chamfered to help evenly distribute the plasma effluents in substrateprocessing region 1070 as the plasma effluents exit the showerhead andpromote even distribution of the plasma effluents and precursor gases.The smaller ID may be placed at a variety of locations alongthrough-holes 1056 and still allow showerhead 1053 to reduce the iondensity within substrate processing region 1070. The reduction in iondensity results from an increase in the number of collisions with wallsprior to entry into substrate processing region 1070. Each collisionincreases the probability that an ion is neutralized by the acquisitionor loss of an electron from the wall. Generally speaking, the smaller IDof through-holes 1056 may be between about 0.2 mm and about 20 mm. Inother embodiments, the smaller ID may be between about 1 mm and 6 mm orbetween about 0.2 mm and about 5 mm. Further, aspect ratios of thethrough-holes 1056 (i.e., the smaller ID to hole length) may beapproximately 1 to 20. The smaller ID of the through-holes may be theminimum ID found along the length of the through-holes. The crosssectional shape of through-holes 1056 may be generally cylindrical,conical, or any combination thereof.

FIG. 3B is a bottom view of a showerhead 1053 for use with a processingchamber according to embodiments. Showerhead 1053 corresponds with theshowerhead shown in FIG. 3A. Through-holes 1056 are depicted with alarger inner-diameter (ID) on the bottom of showerhead 1053 and asmaller ID at the top. Small holes 1055 are distributed substantiallyevenly over the surface of the showerhead, even amongst thethrough-holes 1056 which helps to provide more even mixing than otherembodiments described herein.

An exemplary patterned substrate may be supported by a pedestal (notshown) within substrate processing region 1070 when fluorine-containingplasma effluents arrive through through-holes 1056 in showerhead 1053.Though substrate processing region 1070 may be equipped to support aplasma for other processes such as curing, no plasma is present duringthe etching of patterned substrate according to embodiments.

A plasma may be ignited either in chamber plasma region 1020 aboveshowerhead 1053 or substrate processing region 1070 below showerhead1053. A plasma is present in chamber plasma region 1020 to produce theradical-fluorine from an inflow of the fluorine-containing precursor. AnAC voltage typically in the radio frequency (RF) range is appliedbetween the conductive top portion (lid 1021) of the processing chamberand showerhead 1053 to ignite a plasma in chamber plasma region 1020during deposition. An RF power supply generates a high RF frequency of13.56 MHz but may also generate other frequencies alone or incombination with the 13.56 MHz frequency.

The top plasma may be left at low or no power when the bottom plasma inthe substrate processing region 1070 is turned on to either cure a filmor clean the interior surfaces bordering substrate processing region1070. A plasma in substrate processing region 1070 is ignited byapplying an AC voltage between showerhead 1053 and the pedestal orbottom of the chamber. A cleaning gas may be introduced into substrateprocessing region 1070 while the plasma is present.

The pedestal may have a heat exchange channel through which a heatexchange fluid flows to control the temperature of the substrate. Thisconfiguration allows the substrate temperature to be cooled or heated tomaintain relatively low temperatures (from room temperature throughabout 120° C.). The heat exchange fluid may comprise ethylene glycol andwater. The wafer support platter of the pedestal (preferably aluminum,ceramic, or a combination thereof) may also be resistively heated toachieve relatively high temperatures (from about 120° C. through about1100° C.) using an embedded single-loop embedded heater elementconfigured to make two full turns in the form of parallel concentriccircles. An outer portion of the heater element may run adjacent to aperimeter of the support platter, while an inner portion runs on thepath of a concentric circle having a smaller radius. The wiring to theheater element passes through the stem of the pedestal.

The chamber plasma region or a region in a remote plasma system may bereferred to as a remote plasma region. In embodiments, theradical-fluorine is formed in the remote plasma region and travels intothe substrate processing region where the radical-fluorinepreferentially etches tungsten. Plasma power may essentially be appliedonly to the remote plasma region, in embodiments, to ensure that theradical-fluorine (which may be referred to as plasma effluents) is notfurther excited in the substrate processing region.

In embodiments employing a chamber plasma region, the excited plasmaeffluents are generated in a section of the substrate processing chamberpartitioned from the substrate processing region. The substrateprocessing region, is where the plasma effluents mix and react to etchthe patterned substrate (e.g., a semiconductor wafer). The excitedplasma effluents may also be accompanied by inert gases (in theexemplary case, argon). The substrate processing region may be describedherein as “plasma-free” during etching of the substrate. “Plasma-free”does not necessarily mean the region is devoid of plasma. A relativelylow concentration of ionized species and free electrons created withinthe plasma region do travel through pores (apertures) in the partition(showerhead/ion suppressor) due to the shapes and sizes of through-holes1056. In some embodiments, there is essentially no concentration ofionized species and free electrons within the substrate processingregion. The borders of the plasma in the chamber plasma region are hardto define and may encroach upon the substrate processing region throughthe apertures in the showerhead. In the case of an inductively-coupledplasma, a small amount of ionization may be effected within thesubstrate processing region directly. Furthermore, a low intensityplasma may be created in the substrate processing region withouteliminating desirable features of the forming film. All causes for aplasma having much lower intensity ion density than the chamber plasmaregion (or a remote plasma region, for that matter) during the creationof the excited plasma effluents do not deviate from the scope of“plasma-free” as used herein.

Nitrogen trifluoride (or another fluorine-containing precursor) may beflowed into chamber plasma region 1020 at rates between about 5 sccm andabout 500 sccm, between about 10 sccm and about 300 sccm, between about25 sccm and about 200 sccm, between about 50 sccm and about 150 sccm orbetween about 75 sccm and about 125 sccm in embodiments.

Combined flow rates of fluorine-containing precursor into the chambermay account for 0.05% to about 20% by volume of the overall gas mixture;the remainder being carrier gases. The fluorine-containing precursor isflowed into the remote plasma region but the plasma effluents have thesame volumetric flow ratio, in embodiments. In the case of thefluorine-containing precursor, a purge or carrier gas may be firstinitiated into the remote plasma region before those of thefluorine-containing gas to stabilize the pressure within the remoteplasma region.

Plasma power applied to the remote plasma region can be a variety offrequencies or a combination of multiple frequencies. In the exemplaryprocessing system the plasma is provided by RF power delivered betweenlid 1021 and showerhead 1053. In an embodiment, the energy is appliedusing a capacitively-coupled plasma unit. When using a Frontier™ orsimilar system, the remote plasma source power may be between about 100watts and about 3000 watts, between about 200 watts and about 2500watts, between about 300 watts and about 2000 watts, or between about500 watts and about 1500 watts in embodiments. The RF frequency appliedin the exemplary processing system may be low RF frequencies less thanabout 200 kHz, high RF frequencies between about 10 MHz and about 15 MHzor microwave frequencies greater than or about 1 GHz according toembodiments.

Substrate processing region 1070 can be maintained at a variety ofpressures during the flow of carrier gases and plasma effluents intosubstrate processing region 1070. The pressure within the substrateprocessing region is below or about 50 Torr, below or about 30 Torr,below or about 20 Torr, below or about 10 Torr or below or about 5 Torrin embodiments. The pressure may be above or about 0.1 Torr, above orabout 0.2 Torr, above or about 0.5 Torr or above or about 1 Torraccording to embodiments. Lower limits on the pressure may be combinedwith upper limits on the pressure in embodiments.

In one or more embodiments, the substrate processing chamber 1001 can beintegrated into a variety of multi-processing platforms, including theProducer™ GT, Centura™ AP and Endura™ platforms available from AppliedMaterials, Inc. located in Santa Clara, Calif. Such a processingplatform is capable of performing several processing operations withoutbreaking vacuum. Processing chambers that may implement embodiments ofthe present invention may include dielectric etch chambers or a varietyof chemical vapor deposition chambers, among other types of chambers.

Embodiments of the deposition systems may be incorporated into largerfabrication systems for producing integrated circuit chips. FIG. 4 showsone such system 1101 of deposition, baking and curing chambers accordingto embodiments. In the figure, a pair of FOUPs (front opening unifiedpods) 1102 supply substrate substrates (e.g., 300 mm diameter wafers)that are received by robotic arms 1104 and placed into a low pressureholding areas 1106 before being placed into one of the wafer processingchambers 1108 a-f. A second robotic arm 1110 may be used to transportthe substrate wafers from the low pressure holding areas 1106 to thewafer processing chambers 1108 a-f and back. Each wafer processingchamber 1108 a-f, can be outfitted to perform a number of substrateprocessing operations including the dry etch processes described hereinin addition to cyclical layer deposition (CLD), atomic layer deposition(ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD),etch, pre-clean, degas, orientation and other substrate processes.

The wafer processing chambers 1108 a-f may include one or more systemcomponents for depositing, annealing, curing and/or etching a flowabledielectric film on the substrate wafer. In one configuration, two pairsof the processing chamber (e.g., 1108 c-d and 1108 e-f) may be used todeposit dielectric material on the substrate, and the third pair ofprocessing chambers (e.g., 1108 a-b) may be used to etch the depositeddielectric. In another configuration, all three pairs of chambers (e.g.,1108 a-f) may be configured to etch a dielectric film on the substrate.Any one or more of the processes described may be carried out onchamber(s) separated from the fabrication system shown in embodiments.

The substrate processing system is controlled by a system controller. Inan exemplary embodiment, the system controller includes a hard diskdrive, a floppy disk drive and a processor. The processor contains asingle-board computer (SBC), analog and digital input/output boards,interface boards and stepper motor controller boards. Various parts ofCVD system conform to the Versa Modular European (VME) standard whichdefines board, card cage, and connector dimensions and types. The VMEstandard also defines the bus structure as having a 16-bit data bus anda 24-bit address bus.

System controller 1157 is used to control motors, valves, flowcontrollers, power supplies and other functions required to carry outprocess recipes described herein. A gas handling system 1155 may also becontrolled by system controller 1157 to introduce gases to one or all ofthe wafer processing chambers 1108 a-f. System controller 1157 may relyon feedback from optical sensors to determine and adjust the position ofmovable mechanical assemblies in gas handling system 1155 and/or inwafer processing chambers 1108 a-f. Mechanical assemblies may includethe robot, throttle valves and susceptors which are moved by motorsunder the control of system controller 1157.

In an exemplary embodiment, system controller 1157 includes a hard diskdrive (memory), USB ports, a floppy disk drive and a processor. Systemcontroller 1157 includes analog and digital input/output boards,interface boards and stepper motor controller boards. Various parts ofmulti-chamber processing system 1101 which contains substrate processingchamber 1001 are controlled by system controller 1157. The systemcontroller executes system control software in the form of a computerprogram stored on computer-readable medium such as a hard disk, a floppydisk or a flash memory thumb drive. Other types of memory can also beused. The computer program includes sets of instructions that dictatethe timing, mixture of gases, chamber pressure, chamber temperature, RFpower levels, susceptor position, and other parameters of a particularprocess.

A process for etching, depositing or otherwise processing a film on asubstrate or a process for cleaning chamber can be implemented using acomputer program product that is executed by the controller. Thecomputer program code can be written in any conventional computerreadable programming language: for example, 68000 assembly language, C,C++, Pascal, Fortran or others. Suitable program code is entered into asingle file, or multiple files, using a conventional text editor, andstored or embodied in a computer usable medium, such as a memory systemof the computer. If the entered code text is in a high level language,the code is compiled, and the resultant compiler code is then linkedwith an object code of precompiled Microsoft Windows® library routines.To execute the linked, compiled object code the system user invokes theobject code, causing the computer system to load the code in memory. TheCPU then reads and executes the code to perform the tasks identified inthe program.

The interface between a user and the controller may be via atouch-sensitive monitor and may also include a mouse and keyboard. Inone embodiment two monitors are used, one mounted in the clean room wallfor the operators and the other behind the wall for the servicetechnicians. The two monitors may simultaneously display the sameinformation, in which case only one is configured to accept input at atime. To select a particular screen or function, the operator touches adesignated area on the display screen with a finger or the mouse. Thetouched area changes its highlighted color, or a new menu or screen isdisplayed, confirming the operator's selection.

As used herein “substrate” may be a support substrate with or withoutlayers formed thereon. The patterned substrate may be an insulator or asemiconductor of a variety of doping concentrations and profiles andmay, for example, be a semiconductor substrate of the type used in themanufacture of integrated circuits. Exposed “silicon nitride” of thepatterned substrate is predominantly Si₃N₄ but may include minorityconcentrations of other elemental constituents (e.g. oxygen, hydrogen,carbon). Exposed “silicon oxide” of the patterned substrate ispredominantly SiO₂ but may include minority concentrations of otherelemental constituents (e.g. nitrogen, hydrogen, carbon). In someembodiments, silicon oxide films etched using the methods describedherein consist essentially of silicon and oxygen. “Titanium nitride” ispredominantly titanium and nitrogen but may include minorityconcentrations of other elemental constituents (e.g. nitrogen, hydrogen,carbon). Titanium nitride may consist of titanium and nitrogen.

The term “precursor” is used to refer to any process gas which takespart in a reaction to either remove material from or deposit materialonto a surface. “Plasma effluents” describe gas exiting from the chamberplasma region and entering the substrate processing region. Plasmaeffluents are in an “excited state” wherein at least some of the gasmolecules are in vibrationally-excited, dissociated and/or ionizedstates. A “radical precursor” is used to describe plasma effluents (agas in an excited state which is exiting a plasma) which participate ina reaction to either remove material from or deposit material on asurface. “Radical-fluorine” is a radical precursor which containsfluorine but may contain other elemental constituents. The phrase “inertgas” refers to any gas which does not form chemical bonds when etchingor being incorporated into a film. Exemplary inert gases include noblegases but may include other gases so long as no chemical bonds areformed when (typically) trace amounts are trapped in a film.

The terms “gap” and “trench” are used throughout with no implicationthat the etched geometry has a large horizontal aspect ratio. Viewedfrom above the surface, trenches may appear circular, oval, polygonal,rectangular, or a variety of other shapes. A trench may be in the shapeof a moat around an island of material. The term “via” is used to referto a low aspect ratio trench (as viewed from above) which may or may notbe filled with metal to form a vertical electrical connection. As usedherein, a conformal etch process refers to a generally uniform removalof material on a surface in the same shape as the surface, i.e., thesurface of the etched layer and the pre-etch surface are generallyparallel. A person having ordinary skill in the art will recognize thatthe etched interface likely cannot be 100% conformal and thus the term“generally” allows for acceptable tolerances.

Having disclosed several embodiments, it will be recognized by those ofskill in the art that various modifications, alternative constructions,and equivalents may be used without departing from the spirit of thedisclosed embodiments. Additionally, a number of well-known processesand elements have not been described to avoid unnecessarily obscuringthe present invention. Accordingly, the above description should not betaken as limiting the scope of the invention.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimits of that range is also specifically disclosed. Each smaller rangebetween any stated value or intervening value in a stated range and anyother stated or intervening value in that stated range is encompassed.The upper and lower limits of these smaller ranges may independently beincluded or excluded in the range, and each range where either, neitheror both limits are included in the smaller ranges is also encompassedwithin the invention, subject to any specifically excluded limit in thestated range. Where the stated range includes one or both of the limits,ranges excluding either or both of those included limits are alsoincluded.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural referents unless the context clearly dictatesotherwise. Thus, for example, reference to “a process” includes aplurality of such processes and reference to “the dielectric material”includes reference to one or more dielectric materials and equivalentsthereof known to those skilled in the art, and so forth.

Also, the words “comprise,” “comprising,” “include,” “including,” and“includes” when used in this specification and in the following claimsare intended to specify the presence of stated features, integers,components, or steps, but they do not preclude the presence or additionof one or more other features, integers, components, steps, acts, orgroups.

1. A method of etching tungsten, the method comprising: transferring apatterned substrate into a substrate processing region, wherein thepatterned substrate has a tungsten lining layer coating a high aspectratio trench having a depth more than five times a width of the highaspect ratio trench; flowing a first fluorine-containing precursor intothe substrate processing region while applying a bias plasma power tobombard the patterned substrate with fluorine-containing ions; flowing asecond fluorine-containing precursor into a remote plasma region fluidlycoupled to a substrate processing region via perforations in aperforated plate; forming a remote plasma in the remote plasma region toproduce plasma effluents from the second fluorine-containing precursorand flowing the plasma effluents into the substrate processing regionthrough the perforations; and etching the tungsten lining layer,wherein, after etching the tungsten lining layer, a top sidewallthickness of the tungsten lining layer measured on a sidewall of thehigh aspect ratio trench near the opening of the high aspect ratiotrench is within 20% of a bottom sidewall thickness of the tungstenlining layer measured on the sidewall of the high aspect ratio trenchnear the bottom of the high aspect ratio trench.
 2. The method of claim1 wherein the depth of the high aspect ratio trench is greater than onemicron.
 3. The method of claim 1 wherein the width of the high aspectratio trench is less than one hundred nanometers.
 4. The method of claim1 wherein the operation of forming the remote plasma occurs after theoperation of applying a bias plasma power.
 5. The method of claim 1wherein no bias plasma power is applied during the operation of formingthe remote plasma.
 6. The method of claim 1 wherein the bias plasmapower is between 20 watts and 500 watts.
 7. The method of claim 1wherein the remote plasma is formed by applying a remote plasma powergreater than 50 watts capacitively to the remote plasma region.
 8. Themethod of claim 1 wherein the first fluorine-containing precursorcomprises at least one precursor selected from the group consisting ofatomic fluorine, diatomic fluorine, bromine trifluoride, chlorinetrifluoride, nitrogen trifluoride, hydrogen fluoride, sulfurhexafluoride and xenon difluoride.
 9. The method of claim 1 wherein atemperature of the patterned substrate is between 30° C. and 400° C.during the operation of etching the tungsten lining layer.
 10. A methodof etching tungsten, the method comprising: transferring a patternedsubstrate into a substrate processing region, wherein the patternedsubstrate has a tungsten lining layer coating two adjacent stacks and ahigh aspect ratio trench between the two adjacent stacks; flowing afirst fluorine-containing precursor into the substrate processing regionwhile applying local plasma power which accelerates fluorine-containingions toward the patterned substrate; flowing a secondfluorine-containing precursor into a remote plasma region fluidlycoupled to a substrate processing region via perforations in aperforated plate; forming a remote plasma in the remote plasma region toproduce plasma effluents from the second fluorine-containing precursorand flowing the plasma effluents into the substrate processing regionthrough the perforations; and etching the tungsten lining layer, whereinetching the tungsten lining layer reduces a thickness of the tungstenlining layer on a sidewall of the high aspect ratio trench.
 11. Themethod of claim 10 wherein the first fluorine-containing precursor isthe same as the second fluorine-containing precursor.
 12. The method ofclaim 10 wherein one or both of the two adjacent stacks comprises atleast ten alternating layers of dielectric and tungsten.
 13. The methodof claim 10 wherein etching the tungsten lining layer reduces athickness of the tungsten lining layer at a top rate near the outermostportion of the sidewall of the high aspect ratio trench which is within20% of a bottom rate near the innermost portion of the sidewall of thehigh aspect ratio trench.
 14. The method of claim 10 wherein the secondfluorine-containing precursor is nitrogen trifluoride.
 15. A method ofetching tungsten, the method comprising: transferring a patternedsubstrate into a substrate processing region, wherein the patternedsubstrate has a tungsten lining layer coating a high aspect ratio trenchhaving a depth more than five times a width of the high aspect ratiotrench; flowing a fluorine-containing precursor into the substrateprocessing region while applying local plasma power capacitively betweena perforated plate and a substrate susceptor supporting the patternedsubstrate to create and accelerate fluorine-containing ions toward thepatterned substrate; flowing nitrogen trifluoride into a remote plasmaregion fluidly coupled to a substrate processing region via perforationsin the perforated plate; forming a remote plasma in the remote plasmaregion to produce plasma effluents from the nitrogen trifluoride andflowing the plasma effluents into the substrate processing regionthrough the perforations; and etching the tungsten lining layer, whereinetching the tungsten lining layer reduces a thickness of the tungstenlining layer on a sidewall of the high aspect ratio trench at a top ratenear the outermost portion of the sidewall of the high aspect ratiotrench which is within 20% of a bottom rate near the innermost portionthe sidewall of the high aspect ratio trench.